1. Field of the Invention
The present invention relates to printing apparatus such as a laser printer in which bit map data is created from intermediate data before printing, and a printing data processing method for use with the printing apparatus.
2. Description of the Related Art
There are widely used printing apparatus of the type receiving data (printing data) representing the contents to be printed and the printing format from a host computer, creating from the received data a bit map to be actually output (this step will be referred to as rendering hereinafter), and making printing output of the bit map onto a sheet of paper, for example, (this step will be referred to as shipping hereinafter).
In the printing apparatus of the type shipping an output bit map of 1 page after the rendering process, a memory for holding the output bit map of 1 page is always required. This results in a disadvantage that the memory capacity must be increased, particularly, in printing apparatus with a high degree of output resolution; hence the apparatus are very expensive.
There are also known printing apparatus of the (banding process) type that one page is divided into a plurality of units (bands) smaller than the page, a bit map of 1 band is created through rendering and then subject to shipping, and the rendering process for the next band is started in parallel with the shipping process for the previous band. Such a printing apparatus has a disadvantage that if the rendering time for the next band is longer than the shipping time for the previous band in the parallel process, a print overrun phenomenon occurs.
Another disadvantage is that because a memory for holding the printing data of 1 page is required in addition to the memory for holding the bit map resulted from rendering, the printing data of 1 page cannot be processed (this phenomenon will be referred to as memory deadlock hereinafter) if the memory capacity is deficient.